1. Technical Field
The present invention relates to data communications using contactless identification tags, and contactless communication systems and contactless identification tags which assure security and easy maintenance of contactless identification tags.
2. Related Art
In recent years, various types of contactless IC tags in a sheet configuration or a tag configuration, in which an IC having data is connected to an antenna coil, have been proposed, and they are used, being attached to commercial products, packing boxes or the like to defend them from shoplifting, and used in commercial distribution systems.
Conventionally, systems that use contactless IC tags to detect impacts have been proposed. For example, there is a system that detects that an impact is applied to a package (see Japanese Laid-open Patent Application 2002-150249), wherein an IC tag having an impact sensor (Japanese Laid-open Patent Application 2002-150248) is attached to the package, the impact sensor breaks and its voltage changes when an impact greater than a predetermined level is applied to the IC tag, and a change in the voltage is detected.
However, although the conventional IC tag described above can detect the presence or absence of an impact, it cannot detect the presence or absence of unauthorized access. Further, it cannot prevent data reading or writing through unauthorized access.
A contactless IC tag may have functions, for example, to read an ID (identification) number written in the IC tag, and to write data in a nonvolatile memory in the IC tag. To operate such functions, in general, commands from a reader/writer device are executed. Accordingly, writing data in or reading data from the IC tag can be done if a reader/writer device that can access the IC tag is prepared.
As a result, for example, if stored data includes purchase history and sales history including private personal information and important client information, it is possible that they can be accessed without being noticed by the owner of the IC tag, and the data may be falsified. Even when commands not open to the public are used as commands from a reader/writer device to execute data reading or writing, an analyzer device may be used to analyze communications between the IC tag and the reader/writer device, whereby a method to access the IC tag can be discovered. This poses a serious problem.
Also, data may be encoded to prevent unauthorized access. However, when IC tags are collected and maintained in the factory, there is a possibility that troublesome operations such as decoding (release) may be needed if an access method is encoded.
Accordingly, the present invention has been made by paying attention to the unsolved problems of the conventional technology, and its object is to provide contactless data communication systems and contactless identification tags which can enhance the security against accesses to the contactless identification tags, and facilitate accesses at the time of maintenance.